In preparation of semiconductor, various treatments are repeated such as smoothing of silicon wafer substrate surface, etching to laminate various layers on the substrate and smoothing of the surface after lamination.
In each of these treatment processes, fine particles such as polishing particles, impurities derived from various metals and foreign substances derived from slurry adhere to semiconductor substrate surface. It is known that when semiconductor is manufactured leaving these impurities as they are, risk increases for semiconductor finally obtained to be unsatisfactory.
Therefore, a process to a clean semiconductor substrate surface after these various treatment processes, so to speak a cleaning process is performed.
Liquid property (pH) of a liquid cleaner used in this cleaning process is said preferably to have nearly the same degree as in various treatment solutions used in a prior process. That is, too rapid change in pH at substrate surface in cleaning the semiconductor substrate surface causes gelling of particles at the semiconductor substrate surface, which makes removal difficult or easily generates roughness of semiconductor substrate surface. Therefore, it is preferable that a liquid cleaner used after a process, adopting an alkaline polishing agent or an alkaline etching liquid, is an alkaline type.
However, when cleaning is performed using a conventional liquid cleaner (for example, the liquid cleaners disclosed in JP-A-5-275405, WO 01/071789, JP-A-10-072594, JP-A-2002-020787, JP-A-11-131093-, JP-A-3-219000, etc.), ability to remove impurity derived from various metals (metals themselves, oxides thereof, hydroxides thereof, etc.), which are adhered to semiconductor substrate surface, was not sufficient and further improvement has been required.
The present invention is completed considering such problems of conventional technology. The present invention aims at providing an alkaline liquid cleaner which can efficiently remove fine particles or impurities derived from various metals at semiconductor substrate surface, even when used after a process adopting an alkaline polishing agent or alkaline etching liquid, without generating problems of causing difficult-to-remove gelled particles at the substrate surface or easy generation of rough semiconductor substrate surface.